1. Junior Basic Science 1/25/2011
Wound Healing
Junior Basic Science
1/25/2011

2. 3 Phases of Wound Healing
1. Inflammation- day 1-10
2. Proliferation-5 days-3 weeks
3. Remodeling-3 weeks-1 year

3. Inflammation Phase: Injury
Bleeding and vasoconstriction(5-10min), followed by vasodilation
Plt plug formation and clotting
Fibrin binds the plt plug and forms the provisional matrix (platelets+fibrin+fibronectin)
Platelet degranulation (alpha and dense granules)
-> PDGF and TGF-B
Chemotaxis for inflammation

4. Inflammation PMNs-almost immediately, clear debris
Macrophages-Day 2-3 (essential)
Fibroblast proliferation, endothelial cell proliferation (angiogenesis), and extracellular matrix production, and they recruit and activate additional macrophages.
Lymphocytes

5. Proliferation Phase (5-21 days)
Fibroblasts-enter provisional matrix and initiate collagen synthesis
Prominent cell type during this phase
Macrophages->angiogenesis and neovascularization
Collagen and proteoglycans or ground substance replaces the provisional fibronectin–fibrin matrix

6. Remodeling Phase (3wks-1 year)
Max collagen accumulation at 2-3 weeks. Only remodeling/crosslinking after 3 weeks.
Type III collagen predominates early (days 1-3), but is replaced by type I
6 weeks-80% of final strength and 60% of original strength
8 weeks-max tensile strength (70-80%)

7. Collagen
Need alpha-ketoglutarate, vit C, O2, and iron for hydroxylation of proline, and crosslinking of proline residues
Proline is every 3rd amino acid. Lysine is abundant from hydroxylysine crosslinking
Type I, most common and most abundant in healed wound
D-penicillamine inhibits collagen crosslinking

8. Surgical Wound Healing
Primary Intention-Tensile strength is important in healing closed incisions
Depends on collagen deposition and cross-linking
Secondary Intention-Epithelial integrity is important in healing open wounds
Dependent on granulation tissue (capillaries, fibroblasts and collagen)
Migration from wound edges, sweat glands and hair follicles

9. Essential for wound healing
Moist environment- optimizes epithelial migration
Oxygen delivery- Essential
Avoid edema- edema causes decreased O2 in wounds
Remove necrotic tissue- leads to infection

10. Factors affecting wound healing
Nutrition-Albumin <3
Infection
Foreign body
Drugs
Diabetes
Ischemia
Aging
Radiation
Neuropathy

12. Scars Contain proteoglycans, hyaluronic acid, and water.
Keloids- AD, dark skinned. Collagen goes beyond original scar
Hypertrophic scar- Collagen stays within scar
Treatment: Steroids, silicone, pressure garments, XRT.
Infants heal with little/no scarring-multifactorial, decreased inflammatory response, increase hyaluronic acid?

13. Chronic Wounds
Pressure Sores- pressure over bony area, occurs when tissue pressure exceeds the capillary filling pressure of 25 mm Hg
Tx: Pressure off loading, debridement, myocutaneous flap
Leg ulcers- 90% due to venous insuff.
Tx: Unna boot, elastic wrap
Diabetic foot ulcers- 2nd MTP joint (Charcot’s joint). Neuropathy leads to increased pressure-> Ischemia
Tx: Depends on extent of ulcer

14. Question
The most prominent cell type in the 1st 24 hours of a wound is :
PMN’s
Macrophages
Lymphocytes
Fibroblasts

15. Answer
PMN’s
Most abundant in 1st 24 hrs, help clear debri

16. Question The most prominent cell type day 2-4? PMN’s Macrophages
Lymphocytes
Platelets

17. Answer
Macrophages
Fibroblast proliferation, endothelial cell proliferation (angiogenesis), and extracellular matrix production, and they recruit and activate additional macrophages.

18. Question What is the most prominent cell type at 1 week? PMN’s
Macrophages
Lymphocytes
Fibroblasts

19. Answer
Fibroblasts
-Enter provisional matrix and initiate collagen synthesis. Days 5-21.

20. Question The most predominant type of collagen in the body? I II IIIIV

21. Answer
Type I most common, seen in skin, bone, tendons, and healed wounds I
II Cartilage
III
IV Basement membrane

22. Question Most abundant collagen in healing wound during 1st 24hrs? III
III IV

23. Answer
Type III- Most abundant the first 48hrs, and is then replaced by type I.

24. Question What is the most important cell involved in wound healing?
PMN’s
Macrophages
Lymphocytes
Fibroblasts

25. Answer
Macrophages
Essential, synthesizes cytokines and growth factors necessary for wound healing.

26. Question Maximal tensile strength of a wound occurs at: 3 weeks
3 months

27. Answer
8 weeks- Has 80-90% of original strength

28. Question
What vitamin can you give to prevent the negative affects on wound healing? A D O K

29. Answer
Vitamin A
25,000 UI daily

30. Question Peripheral nerves regenerate at: 0.01mm/year 0.1mm/day

31. Answer
1mm per day

32. Question
The most important factor in the healing wounds by secondary intention is:
Tensile strength
Epithelial integrity
Platelet activating factor
cocaine

33. Answer
Epithelial integrity- epithelial cells migrate from hair follicles, wound edges and sweat glands.

34. Question
The most important factor in the healing wound by primary intention is:
Double cheeseburger from McDonalds
Tensile strength
Epithelial integrity
Platelet activating factor

35. Answer Tensile strength, not double cheeseburger
This is created by collagen cross linking

36. Question
The dressing change regimen that will produce maximal debridement is:
Wet-to-dry dressing changes with saline.
Dressing changes with Xeroflo.
Dressing changes with silver sulfadiazine.
Dressing changes with an occlusive dressing.

37. Answer
Maximal debridement is accomplished when the dressing is changed utilizing wet-to-dry dressings. Enzymatic agents, such as collagenase, may augment the debriding effect of wet to dry dressing changes.

38. Question Hypoxia in a wound stimulates: collagen synthesis contraction
ovulation
angiogenesis
epithelialization

39. Answer
Angiogenesis

40. Question
Cofactors necessary for successful hydroxylation of proline include all the following except:
Vitamin C.
Magnesium.
Ferrous ion.
α-Ketoglutarate.
Oxygen.

41. Answer
Magnesium

42. Question
Local factors which invite wound infection include all of the following except:
Foreign material.
Radiation injury.
Poor circulation.
Disruption of fascia.
Hematoma.

43. Answer Disruption of fascia
Depth of injury into the fascia has not been identified as a wound characteristic that predisposes to infection

44. Question Significant collagen synthesis first begins in a wound at:
2 to 4 weeks.
7 to 10 days.
0 to 12 hours.
12 to 24 hours.
3 to 5 days.

45. Answer
Significant collagen synthesis begins in a wound at 3 to 5 days.